The present invention relates to a surface inspection apparatus and a method thereof for discriminatingly inspecting defects such as scratches and foreign objects that arise in the flattening process in which polishing or grinding working technique is applied in semiconductor manufacturing process or magnetic head manufacturing process.
As for the prior art for discriminatingly inspecting a foreign object that adheres on a semiconductor wafer on which a circuit pattern has been formed from the circuit pattern, Japanese Unexamined Patent Publication No. H3-102248 (prior art 1) and Japanese Unexamined Patent Publication No. H3-102249 (prior art 2) have been known. In detail, a method is described in the prior art 1 and the prior art 2, in which a foreign object on a semiconductor substrate is detected by means of a first photoelectric conversion element with emphasis by use of a slant illumination, and an edge of a circuit pattern that is the background on the semiconductor is detected by means of a second photoelectric conversion element with emphasis by use of an epi-illumination, the foreign detection signal obtained from the above-mentioned first photoelectric conversion element is divided by the detection signal obtained from the second photoelectric element to thereby emphasize the foreign object detection signal, and thus the foreign object is detected.
As for the prior art for discriminatingly inspecting adherent foreign objects on the silicon wafer surface from the crystalline defect on the surface, Japanese Unexamined Patent Publication No.H9-304289(prior art 3) has been known. In detail, a discriminating inspection method is described in the prior art 3, in which an inspection apparatus is provided with a low angle light receiving system that makes an elevation angle of equal to or smaller than 30 degrees with respect to the surface of the silicon wafer and a high angle light receiving system that makes an elevation angle of larger than that of the low angle light receiving system, the scattered light obtained by irradiating a laser light onto the surface of the silicon wafer approximately perpendicularly is received by the low angle light receiving system and the high angle light receiving system, wherein the light received only by the high angle light receiving system is attributed to the crystalline defect, and the light that is received by both the low angle light receiving system and the high angle light receiving system is attributed to the adherent foreign object.
As for the prior art for discriminatingly inspecting the foreign object or flaw on the surface of a semiconductor wafer from a small dot dimple that is too small to cause the problem in forming of a circuit pattern without mis-discrimination, Japanese Unexamined Patent Publication No. H11-142127 has been known (prior art 4). In detail, an inspection method is described in the prior art 4, in which a low incident angle light and a high incident angle light having wavelengths that are different each other are irradiated in focus on the same point on the surface of a semiconductor wafer with a low incident angle and a high incident angle respectively, the scattered light of two wavelengths from the focused point is received separately and photoelectrically converted, and thus the foreign object and the flaw is discriminated from the dot dimple on the surface of the semiconductor wafer, wherein the intensity difference between signals is utilized, that is, the principle that the intensity of the light irradiated with a low incident angle and scattered from the dot dimple is weak is utilized.
Aside from the above, CMP (Chemical Mechanical Polishing) has been known as a typical (flattening) work technique applied on a work target (for example, insulating film) in the semiconductor manufacturing process or magnetic head manufacturing process. CMP is a (flattening) technique in which free abrasive grains consisting of a material such as silica is spread on a polishing pad and the surface of the work target is polished. Another grinding work technique has been known, in which a work target is polished with use of a pad on which grinding grains consisting of a material such as diamond are embedded fixedly. In such polishing or grinding process, scratches having various configuration, that are polishing flaw or grinding flaw, can be formed on the surface of a work target (for example, an insulating film on a semiconductor substrate (wafer)). If scratches having various configuration are formed on the surface of a work target in the semiconductor manufacturing process or the magnetic head manufacturing process as described hereinabove, a scratch causes insufficient etching in wiring forming and causes the defect such as short-circuit. To eliminate such defect, it is necessary that the polished wafer surface or ground surface is observed after polishing or grinding to monitor the occurrence of scratches having various configuration, and polishing condition or grinding condition must be reviewed correspondingly to the configuration of scratches if the scratch occurs frequently. Furthermore, the foreign object also causes the defect such as defective insulation and short-circuit of wiring to be formed thereon.
If the foreign object occurs frequently, a countermeasure such as cleaning of an equipment is required, and at that time the countermeasure is different from that for scratching. In other words, it is required to monitor discriminatingly between the foreign object and scratch having various configuration, and to apply a countermeasure relevant to the foreign object or scratch in polishing process or grinding process applied on a work target (for example, an insulating film on a semiconductor substrate).
However, any of the prior arts 1 to 4 does not involve inspection for discriminating between the scratch having various configuration and adherent foreign object on the surface of a work target in polishing process or grinding process applied on the work target (for example, an insulating film on a semiconductor substrate).
Generally, because the width W of the scratch having various configuration ranges as small as from 0.2 μm to 0.4 μm, and the depth D ranges as very shallow as from several nm to the deepest 100 nm, a worker visually discriminates between the scratch having various configuration and the foreign object by use of an electron microscope conventionally, but such visual observation requires much time. As the result, the countermeasure for scratch or foreign object is devised delayingly, and many wafers are polished under bad condition to result in much loss of profit.